@socket.io/component-emitter

What is @socket.io/component-emitter?

@socket.io/component-emitter is a lightweight event emitter library that allows you to create and manage custom events. It is commonly used in applications where you need to implement an event-driven architecture, such as in real-time web applications.

What are @socket.io/component-emitter's main functionalities?

Event Emission

This feature allows you to emit custom events and listen for them. In the code sample, an event named 'event' is emitted, and a listener logs a message to the console when the event occurs.

const Emitter = require('@socket.io/component-emitter');
const emitter = new Emitter();
emitter.on('event', function() {
  console.log('An event occurred!');
});
emitter.emit('event');

Event Removal

This feature allows you to remove specific event listeners. In the code sample, the listener for the 'event' is removed before the event is emitted, so no message is logged to the console.

const Emitter = require('@socket.io/component-emitter');
const emitter = new Emitter();
function response() {
  console.log('An event occurred!');
}
emitter.on('event', response);
emitter.off('event', response);
emitter.emit('event');

Once Event Listener

This feature allows you to add a listener that will be called at most once for a particular event. In the code sample, the listener logs a message only the first time the 'event' is emitted.

const Emitter = require('@socket.io/component-emitter');
const emitter = new Emitter();
emitter.once('event', function() {
  console.log('This will only log once');
});
emitter.emit('event');
emitter.emit('event');

Other packages similar to @socket.io/component-emitter

events

The 'events' package is the built-in Node.js module for handling events. It provides a similar event-driven architecture and is widely used in Node.js applications. Compared to @socket.io/component-emitter, 'events' is more feature-rich and is part of the Node.js core.

eventemitter3

The 'eventemitter3' package is a high-performance event emitter for Node.js and the browser. It is similar to @socket.io/component-emitter in terms of functionality but is optimized for performance and has a smaller footprint.

mitt

The 'mitt' package is a tiny (~200 bytes) functional event emitter. It provides a minimal API for event handling and is suitable for use in both Node.js and browser environments. Compared to @socket.io/component-emitter, 'mitt' is more lightweight and has a simpler API.

README

@socket.io/component-emitter

Event emitter component.

This project is a fork of the component-emitter project, with Socket.IO-specific TypeScript typings.

Installation

$ npm i @socket.io/component-emitter

API

Emitter(obj)

The Emitter may also be used as a mixin. For example a "plain" object may become an emitter, or you may extend an existing prototype.

As an Emitter instance:

import { Emitter } from '@socket.io/component-emitter';

var emitter = new Emitter;
emitter.emit('something');

As a mixin:

import { Emitter } from '@socket.io/component-emitter';

var user = { name: 'tobi' };
Emitter(user);

user.emit('im a user');

As a prototype mixin:

import { Emitter } from '@socket.io/component-emitter';

Emitter(User.prototype);

Emitter#on(event, fn)

Register an event handler fn.

Emitter#once(event, fn)

Register a single-shot event handler fn, removed immediately after it is invoked the first time.

Emitter#off(event, fn)

• Pass event and fn to remove a listener.
• Pass event to remove all listeners on that event.
• Pass nothing to remove all listeners on all events.

Emitter#emit(event, ...)

Emit an event with variable option args.

Emitter#listeners(event)

Return an array of callbacks, or an empty array.

Emitter#hasListeners(event)

Check if this emitter has event handlers.

License

MIT

Changelog

3.1.2 (2024-04-26)

Bug Fixes

• point towards the CommonJS types (e6aa1a3)